The present invention relates to a pneumatic fastener driving tool for ramming down or driving fasteners such as nails etc. into an intended location, and more particularly, to the type thereof having an improved air exhaust arrangement.
A pneumatic fastener driving tool urges an internal drive piston downwardly through a drive source such as a compressed air for driving a nail etc. into a wall or other intended location. The drive piston is reciprocally movable, and therefore, the compressed air applied to an upper portion of the drive piston must be discharged to an atmosphere during return stroke of the piston. To this effect, an exhaust port is formed at an upper portion of the driving tool for allowing the compressed air to be discharged outside.
One example of a conventional pneumatic fastener driving tool is shown in FIG. 1. The tool generally includes a main frame 105, a body portion 102 in which a ramming or driving mechanism such as a drive piston is disposed, and a casing 103 for encasing therein a compressed air exhausting arrangement. The casing 103 is formed with an exhaust port 108 for discharging compressed air therethrough. Further, a cover member 101 formed of a steel plate is attached on an upper portion of the casing 103 by means of a bolt 104 for covering the upper portion of the casing 103 and for defining the exhaust port 108.
With this structure, the cover member 101 generally direct the exhausted compressed air in one direction. Therefore, in some cases of operation modes, exhaust air may be impinged on an operator's face, and the exhaust air may be fling up dust. Further, since the cover member 101 is formed of the steel plate, a sympathetic vibration may occur in relation to the casing 103 due to vibration attendant to the air discharge. Therefore, uncomfortable air exhaust noise may be generated, and crack may also be generated at a fastening portion of the cover member 101 around the bolt 104.
In order to avoid the above described problem, other conventional pneumatic fastener driving tools have been proposed. For example, a driving tool shown in FIG. 2 includes a main frame 105A, a body portion 102A in which a drive piston 107A is reciprocally disposed, and a casing 103A. the driving tool is further provided with a tubular member 101A instead of the cover member 101 shown in FIG. 1. The tubular member 101A is formed with an exhaust passage 108A in communication with an internal space of the casing 103A. The tubular member 101A has an inner portion engageable with an inner surface of the casing 103A, and a coil spring 109A is disposed inside the casing 103A for urging the tubular member 101A in a direction to contact with the inner surface of the casing in order to prevent the air from being leaked through mating surfaces between the tubular member 101A and the casing 103A. The tubular exhaust member 101A has another end formed with an exhaust port directing in a horizontal direction. Therefore, the tubular exhaust member 101A is rotatable about its axis by depressing the same against the biasing force of the spring 109A, so that the air discharging direction can be changed to a desired direction.
Further, according to a still another type conventional arrangement shown in FIG. 3, an air exhaust member 101B formed with an exhaust port is secured to a casing 103B by a bolt 104. The air exhaust member 101B becomes rotatable by unfastening the bolt 104, so that the angular position of the exhaust port can also be changed. Thus, the compressed air in a body portion 102B can be discharged to a desired direction. An O-ring 106 is provided to provide a hermetical seal between the air exhaust member 101B and the casing 103B in order to avoid air leakage into directions other than the exhaust port. Incidentally, reference numerals 105B and 107B designate a main frame and a drive piston, respectively.
In the conventional driving tool shown in FIG. 2, the casing 103B must be detached from the body portion 102A in order to attach the exhaust tubular member 101A, since the latter is supported to the casing 103B at an internal portion thereof. Further, in the another conventional driving tool shown in FIG. 3, the air exhaust member 101B can not be rotated unless the bolt 104 is unfastened. Therefore, a tool is required for unfastening the bolt 104. Moreover, the air exhaust member 101B must be secured by the bolt 104, and the O-ring 106 is additionally required. Therefore, greater numbers of the components are required to render the overall device expensive. Further, even though the air discharging direction can be changed, the problem of noise and crack generation as described above has not yet been solved.